Figure 4 Electrophysiological study in patient III‐24. (A) Median nerve motor conduction study (upper trace, wrist stimulation; lower superimposed traces, elbow stimulation) showing prolonged distal motor latency (DML), low forearm motor conduction velocity (MCV), normal terminal latency index (TLI) and compound muscle action potential (CMAP) attenuation with preserved morphology. Changes in CMAP duration, amplitude or morphology on distal and proximal stimulation are absent. (B) Poor recruitment during full effort from the gluteus medius muscle. (C) Samples of long duration and high‐amplitude motor unit potentials from the gluteus medius muscle.